1. Field of the Invention
This invention generally relates to hanger bars and their installation. In particular, it relates to a one-piece hanger bar structure useful in mounting suspended light fixtures between spaced supports.
2. Related Art
Hanger bars are frequently used to mount light fixtures between spaced supports or joists. The ends of the hanger bars are fastened to vertical faces of the supports by nailing or other means, and the light fixture is suspended between spaced hanger bars. The distance between supports or joists can vary to a considerable degree. Therefore, it is desirable for the hanger bars to have an adjustable length.
Hanger bars constructed from two interfitting members that slide in a telescoping manner have been introduced to provide the desired adjustable-length feature. However, this two-piece construction has certain drawbacks. First, the manufacture of the two pieces is relatively complicated and costly. Second, the two pieces must be assembled subsequent to manufacture, thereby adding additional cost and complexity. Third, the two-piece design is prone to "sag" or be deflected by the weight of the suspended light fixture.
Therefore it would be desirable to provide a hanger bar construction that is adjustable in length, is relatively inexpensive to manufacture, does not require a subsequent assembly of multiple components, and is of sufficient strength and rigidity so as to resist sagging.
U.S. Pat. Nos. 4,149,693 and 3,597,889, both to LoNigro, each disclose a strap-iron support bar for mounting a junction box between inverted T-irons of a hanging grid-type ceiling. The ends of the support bar are bent to form U-shaped hooks that fit over the inverted T-irons. The length of the support bar is not disclosed as being adjustable.
U.S. Pat. No. 1,791,480 to Smith et. al. discloses a bar for hanging electrical fixtures. The bar includes a plurality spaced of nail holes that permit the position of the bar to be shifted to locate the light fixture in the desired location. The hanger bar is not designed to be mounted to the vertical surfaces of the ceiling joists, and is not disclosed as having an adjustable length.